<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>06_计算器练习</title>
</head>
<body>
<input type="text" placeholder="请输入数字1" id="i1"><br>
<input type="text" placeholder="请输入数字2" id="i2"><br>
<button onclick="calc('+')">加</button>
<button onclick="calc('-')">减</button>
<button onclick="calc('*')">乘</button>
<button onclick="calc('/')">除</button><br>
<h4>运算结果：<span></span></h4><br>
<script>
    function calc(o){
        //1.获取用户在输入框中输入数字
        let n1=document.getElementById('i1').value;
        let n2=document.getElementById('i2').value;
        //2.将获取到的字符串转为字符类型
        n1=parseFloat(n1);
        n2=parseFloat(n2);
        //3.获取用来显示结果的span元素
        let spanE=document.querySelector('span');
        console.log(spanE);
        //4.根据调入方法时传入的运算符进行指定的四则运算
        switch (o){
            case '+':
                spanE.innerHTML=n1+n2;
                break;
            case '-':
                spanE.innerHTML=n1-n2;
                break;
            case'*':
                spanE.innerHTML=n1*n2;
                break;
            case '/':
                if (n2!=0){
                    spanE.innerHTML=n1/n2;
                }
                else{
                    alert('除数不能为0')
                }
        }

    }
</script>
</body>
</html>